This invention relates to a direct injected internal combustion engine and more particular to an improved combustion chamber for such an engine.
There continues to be a demand for improved performance in internal combustion engines. Although alternative power sources have been considered, internal combustion engines still offer a very efficient and environmentally friendly supply of power. However, in many applications for engines, such as in powering vehicles, the engine is required to run over widely varying load and speed ranges. It is very difficult to ensure good performance, maximum fuel economy, and effective emission control under all such running conditions.
Various devices have been proposed so as to improve the performance of an engine and also to improve its flexibility. In order to obtain better combustion control, it has been proposed to employ direct cylinder injection. With direct cylinder injection, the fuel is injected directly into the combustion chamber of the engine. This has a number of advantages.
However, in spite of the advantages, there is still a reluctance to employ direct cylinder injection for several reasons. The first of these is the cost of the injector. When the injector must be exposed, at least in part, to the combustion conditions in the combustion chamber, the cost of the injector can become relatively high. More importantly, however, there is a significant problem in the positioning of the fuel injector.
The problem of positioning the fuel injector for direct injection is also complicated when other features of the engine are designed so as to achieve good specific performance. For example, the use of such features as multiple valves, overhead cam shafts and the like, increases the difficulty in positioning a fuel injector for direct injection. It is a still further object of this invention to provide an improved fuel injector position for such an engine wherein direct injection can be enjoyed.
It, therefore, is a principle object of this invention to provide an improved fuel injector position for an engine embodying overhead valves and direct cylinder injection.
One of the important advantages of using direct cylinder injection is that it lends itself to achieving stratification in the combustion chamber. A conventional engine has a homogeneous fuel/air mixture in the entire combustion chamber at the time of combustion, regardless of the load. This means that the cylinder is overcharged with fuel under most running conditions.
Thus, attempts to provide what is referred to as "lean burn" have been resorted to. By running on a lean burn condition, the entire combustion chamber is not charged with a homogeneous, stoichiometric fuel/air mixture. If there can be provided a stoichiometric patch of fuel at the spark gap at the time of firing, the entire cylinder need not be charged with a stoichiometric mixture. This has obvious advantages from the point of not only fuel economy, but also exhaust emission control.
However, in order to achieve this stratification, it is necessary to have the combustion chamber appropriately configured and to have the fuel injector position so as to spray into the optimum position to achieve stratification. As noted above, this problem is particularly acute when utilizing multiple valves and overhead cam shafts.
Therefore it is a still further object of this invention to provide an improved fuel injector position for an engine having direct injection and wherein stratification can be achieved.
It is fairly common to employ a combustion chamber configuration that employs four valves per cylinder. Such four valve per cylinder engines employ two intake valves and two exhaust valves for each cylinder.
By using multiple, but smaller, valves, the engine can be run at higher speeds and greater power outputs obtained. This is because the valve train has lower inertia than when utilizing single large valves. Also, the utilization of multiple valves permits the use of various induction control arrangement that can achieve certain types of flow patterns in the combustion chamber under some running conditions.
It is desirable if turbulence can be maintained in the combustion chamber under low speed and low load conditions. By providing a turbulent charge in the combustion chamber, flame propagation can be improved and complete combustion insured.
However, if turbulence is generated, then there is a restriction to the air flow and maximum power output will be sacrificed. Therefore, various types of flow control valves have been provided in the induction system for achieving turbulence under some conditions and free breathing under maximum power and load conditions.
Although two intake valves per cylinder are common, there is a distinct advantage in employing at least three intake valves for the engine. The added third valve can still further augment the breathing capability of the engine and have other advantages. However, with an engine having three intake valves and particularly one intake valve that is positioned on a plane that contains the axis of the cylinder bore, and which extends across from the intake side to the exhaust side, the positioning of the fuel injector becomes difficult.
Also, it is important to position the fuel injector relative to the intake passage so that the intake air flow can assist in maintaining stratification. This also becomes a problem with an engine having a centrally positioned intake valve, as is typical with three intake valve engines.
It is, therefore, another principle object of this invention to provide an improved combustion chamber arrangement for a direct injected engine having an intake valve that is disposed on a plane that contains the center of the cylinder bore axis and which extends across from the intake side to the exhaust side.
It is a still further object of this invention to provide an improved fuel injector position for such an engine wherein direct injection can be enjoyed.